Stem Cells HHMI Outreach Program Description: A colony of embryonic stem cells. 10X. Image in the Public Domain. Description: (A) Human ESCs; (B) Neurons derived from Human ESCs. Images courtesy of Nissim Benvenisty. HHMI Outreach Program

Stem Cells and Regenerative Biology Major Topics for Discussion: What are Stem Cells? What are the major types of Stem Cells and where are they found? Advantages & Disadvantages to ESCs and ASCs Why are Stem Cells so very important? The Controversy over Stem Cells?

What are Stem Cells? Stem Cells are extraordinary because: They can divide and make identical copies of themselves over and over again through mitotic cell division (Self-Renewal) They have the potential to differentiate into a diverse range of specialized cell types (Potency)

The Major Types of Stem Cells Embryonic Stem Cells From blastocysts left over from In-Vitro Fertilization (IVF) in the laboratory From aborted fetuses B. Adult Stem Cells Stem cells have been found in the blood, bone marrow, liver, kidney, cornea, dental pulp, umbilical cord, brain, skin, muscle, salivary gland . . . Function: repair system for the body, replenishing specialized cells, but also maintaining the normal turnover of regenerative organs, such as blood, skin or intestinal tissues.

Potency Definitions Totipotent cells can differentiate into embryonic and extraembryonic cell types stem cells are produced from the fusion of an egg and sperm cell. Cells produced by the first few divisions of the fertilized egg are also totipotent. Pluripotent stem cells that are the descendants of totipotent cells and can differentiate into each of the more than 200 cell types of the adult body can develop when given sufficient and necessary stimulation for a specific cell type. They do not contribute to the extra-embryonic membranes or the placenta.

Potency Definitions Multipotent stem cells can produce only cells of a closely related family of cells (e.g. hematopoietic stem cells differentiate into red blood cells, white blood cells, platelets, etc.). Unipotent cells can produce only one cell type, but have the property of self-renewal which distinguishes them from non-stem cells (e.g. muscle stem cells).

http://commons.wikimedia.org/wiki/Image:Stem_cells_diagram.png

Advantages and Disadvantages to Embryonic and Adult Stem Cells. Embryonic S.C. Adult S.C. “Pluripotent” (can become any cell) “Multipotent” (“can become many but not any”) Stable. Can undergo many cell divisions. Less Stable. Capacity for self-renewal is limited. Easy to obtain but blastocyst is destroyed. Difficult to isolate in adult tissue. Possibility of rejection?? Host rejection minimized

Reprinted with permission of Do No Harm Reprinted with permission of Do No Harm. Click on image for link to website.

Why is Stem Cell Research So Important to All of Us? Stem cells allow us to study how organisms grow and develop over time. Stem cells can replace diseased or damaged cells that can not heal or renew themselves. We can test different substances (drugs and chemicals) on stem cells. We can get a better understanding of our “genetic machinery.”

Reprinted with permission from the Univ. of Kansas Medical Center Reprinted with permission from the Univ. of Kansas Medical Center. Click on image for link to originating website.

What Human Diseases are Currently Experimentally Being Treated with Stem Cells? Parkinson’s Disease Leukemia (Bone Marrow Transplants) Skin Grafts resulting from severe burns Stem Cell Therapy has the Potential to: Regenerate tissues/organs Cure diseases like diabetes, multiple sclerosis, etc.

Why the Controversy Over Stem cells? Embryonic Stem cells are derived from extra blastocysts that would otherwise be discarded following IVF. Extracting stem cells destroys the developing blastocyst (embryo). -Questions for Consideration- Is an embryo a person? Is it morally acceptable to use embryos for research? When do we become “human beings?” For further information: http://bioethics.gov/cgi-bin/bioeth-counter